1. Field of the Invention
The present invention relates to an improved alignment gauge, also referred to as a tram instrument, for checking the alignment of a vehicular frame. More particularly, the invention relates to an alignment gauge which can be easily and reliably used by body shop personnel to check the alignment of a car frame.
2. Description of the Prior Art
Various tools have been devised and used for decades to check the accuracy of reference points on an object by comparing measured distances with published data, or by comparing one set of measurements with other measurements taken for the same or similar reference points. A device for accomplishing this purpose, which has often been referred to as a trammel or tram gauge, generally comprises an elongate beam and one or more movable pins or needle indicators along the beam to measure or compare the distance between the reference points. A foldable trammel is disclosed in U.S. Pat. No. 916,912, and U.S. Pat. No. 1,653,016 discloses a mason's scale for leveling brick walls. U.S. Pat. No. 2,532,376 discloses a beam trammel with a cam-type locking head for temporarily fixing the needle indicator or pin along the trammel beam.
Unique problems are encountered when devising and using an adjustment gauge for checking various reference points on a frame of an automobile. Those skilled in the art appreciate that various publications list the correct distance between selected points on a car's frame, and gauges have long been used on cars involved in accidents to check those distances. An alignment gauge for use on car frames should be highly portable, relatively inexpensive and should be capable of being easily and reliably used by relatively inexperienced body shop personnel. U.S. Pat. No. 1,804,448 discloses a "tracking gauge" for detecting faults in the alignment of a vehicle's wheels. U.S. Pat. No. 3,810,313 discloses multiple frame gauges for suspending from a vehicular frame for checking misalignment.
In recent years, vehicular frames have generally been fabricated according to unibody techniques, so that the frame of the vehicle is structurally a unitary member, rather than comprising a plurality of frame components which are bolted together. This unitary construction emphasizes the neccessity for accurately checking the frame alignment, since a bent unibody frame can be expensive to correct. U.S. Pat. No. 4,321,754 discloses a vehicle alignment device suitable for use on a unibody-contructed automobile, and particularly one which includes a McPherson Strut system. U.S. Pat. No. 4,375,131 discloses the use of three gauges, each with a floor engagable base and upwardly projecting pins for checking the spacing between opposite sides of vehicle frame components relative to a longitudinal frame centerline. An elaborate frame alignment gauge is disclosed in U.S. Pat. No. 4,561,187, which is used by driving a vehicle onto a rack such that the centerline of an undamaged vehicle is directly above the elongate datum member. Plumb bob units are thereafter suspended from reference points on the frame, and slides and telescoping arms on the unit are adjusted to check the alignment of the frame.
A vehicular alignment gauged with a rectangular-shaped frame including a base for floor support is manufactured by Arn-Wood Co., Inc. This type of gauge is difficult and time consuming to set up, and has limited versatility. One of the more popular vehicular frame alignment gauges used today is the Mo-Clamp tram instrument manufactured by Pull-It Corp. This unit can be used to check dimensions between control points or reference points on the suspension and mechanical components of the vehicular frame. A bubble level is provided for horizontal leveling of the tram beam. A disadvantage of this gauge is that the vehicle centerline to left side reference point measurements cannot be easily compared with the vehicle centerline to right side reference point measurements. Vertical measurements between reference points also cannot be easily taken, and measurements or comparison between key reference points, such as a reference point on the cowl and a reference point on a bumper support, cannot be practically generated.
The disadvantages of the prior art are overcome by the present invention, and an improved alignment gauge is hereinafter disclosed for checking the alignment at selected locations on a vehicular frame.